For the control of functions in apparatuses, e.g. for the processing of audio or video signals, use is often made of operating elements which communicate numerical control values in a specific range of values to the apparatus which performs the actual function. These operating elements generally have an actuation element to which a sensor element is fitted. Rotary encoders or linearly actuated sensor elements are usually used for actuation. The position of the sensor element is detected by a pickup, which generates a position signal corresponding to the position. A converter then converts the position signal linearly into numerical control values.
For a particularly finely graded processing, use is made e.g. of a converter with a resolution of 16 bits, which corresponds to a range of values from 0 to 65535. Often, a boosting or attenuation function is intended to be carried out by means of a single operating element. This is achieved by the declaration of a virtual central position or zero position for a value in the middle of the entire range of values. Setting values below the middle value thus declared then leads to an attenuation, and values above the middle value correspondingly lead to a boosting of the processed signal.
In the case of a linear conversion of the position of the actuation element, relatively small corrections of the processed audio or video signal are associated with small alterations of the position of the actuation element. Relatively large corrections of the processed audio or video signal are correspondingly associated with large alterations of the position of the actuation element.
In many cases, the signal to be processed only requires slight corrections. In this case, the extreme ranges of values, at 0 and 65535 in the abovementioned example, are only rarely utilized.
Depending on the design, the linear conversion can have the effect that the operability becomes difficult in the region of small corrections since even very small movements of the actuation element lead to corresponding changes in value. In the case of a large correction, the operator has to perform large movements in order to set the high correction value desired. Under certain circumstances, the large movement required cannot be performed rapidly enough.
This problem can be solved through the combination of a coarse regulator and an associated fine regulator. However, this is often not possible or desired for cost reasons or for space reasons and owing to the poorer operability.